Following a severe cardiac episode pumping volumes drop upwards of 50%. With such poor perfusion vital organs such as the brain, liver and kidneys are quickly damaged. Often heart transplant is not a viable solution due to the immune response to the foreign tissue as well as the limited availability of donor organs. Efforts to produce even temporary artificial hearts have largely been unsuccessful.
A deficiency common to artificial heart devices has been excessive thrombosis and embolization. These life threatening occurrences result from crushing or shearing blood elements by mechanical means. The use of rigid construction materials for vanes, screws and valves is principally responsible for these problems.
The use of differential pressures on a plenum to force blood from a cavity in itself lessens the cell damage; however, the need for ball or flap valves to prevent back flow merely shifts the location of cellular damage. Appreciable stagnation within the bladder also characterizes this design, thereby facilitating thrombosis. In addition, the need for an external compressor diminishes the quality of life and leaves the recipient vulnerable to infection via the tubes exiting the chest cavity. Plenum type designs have been utilized previously and are exemplified by U.S. Pat. Nos. 4,058,857 (Runge et al 1977), 4,994,078 (Jarvik 1991), and 5,286,849 (Kolffet al 1994), which are incorporated herein by reference.
High speed rotary and helical pumps have often suffer reliability problems and exacerbate the problems of aforementioned corpuscular damage. High speed rotary and helical pumps have been developed extensively; U.S. Pat. Nos. 4,704,121 (Moise 1987), 4,927,407 (Dorman 1990) and 4,995,857 (Arnold 1991) are examples of these types of design and are incorporated herein by reference.
Another approach to subsidizing cardiac output has involved centrifugal pumps. A centrifugal pump is defined to include radial flow and axial flow propeller pumps. The flow dynamics and properties of centrifugal pumps are well established, G. F. Wislicenius reviewed the subject in the Mechanical Engineers Handbook (1951) ed. L. S. Marks, McGraw Hill, N.Y., N.Y. Sealing of the shaft and bearings, between the drive mechanism and the propeller is of considerable importance in consideration of corpuscular damage.